Airmatic Issue S500 2006 W221

Two weeks back I started hearing hissing sound from the front side of the car and two days back found left side of the car lowered, when I started the car found MALFUNCTION message for airmatic. Drove to a garage, they replaced the left strut, assured all will be ok now, the next morning found the car lowered all the way down from the left side, once started, got a message "vehicle rising please wait", the car balanced out on all sides, but when turned off the left side lowers. Is it a leak in the left valve somewhere because the strut has been replaced, please advise.
Thank you.







